Chapter 5: Photosynthesis

Question 1

What is the primary purpose of photosynthesis?

Answer 1

The primary purpose of photosynthesis is to convert light energy into chemical energy in the form of glucose.

Question 2

What are the inputs and outputs of photosynthesis?

Answer 2

Carbon dioxide (CO2) and water (H2O). Outputs: Glucose (C6H12O6), oxygen (O2), and water (H2O).

Question 3

Where does photosynthesis primarily occur in plants?

Answer 3

Photosynthesis primarily occurs in the chloroplasts, specifically within the mesophyll cells of leaves.

Question 4

What are the two main stages of photosynthesis?

Answer 4

The two main stages of photosynthesis are the light-dependent stage and the light-independent stage (also known as the Calvin cycle).

Question 5

Describe the light-dependent stage of photosynthesis.

Answer 5

The light-dependent stage occurs on the thylakoid membranes of chloroplasts. It requires light and involves the splitting of water molecules into oxygen and hydrogen. This stage produces ATP and NADPH, which are used in the light-independent stage.

Question 6

What are the inputs and outputs of the light-dependent stage of photosynthesis?

Answer 6

Inputs: 12Water (H2O), 12NADP+, and 18ADP + Pi. Outputs: 6Oxygen (O2), 12NADPH, and 18ATP.

Question 7

Where does the light-independent stage of photosynthesis occur, and what are its inputs and outputs?

Answer 7

The light-independent stage occurs in the stroma of chloroplasts. Inputs: 6Carbon dioxide (CO2), 12NADPH, and 18ATP. Outputs: Glucose (C6H12O6), 12NADP+, 18ADP + Pi, and 6water (H2O).

Question 8

What is the role of enzymes and coenzymes in photosynthesis?

Answer 8

Enzymes catalyze the reactions of photosynthesis, while coenzymes such as NADPH and ATP assist in transferring energy and hydrogen ions between reactions.

Rubisco in light independent

Question 9

How do plants utilize the glucose produced during photosynthesis?

Answer 9

Plants use glucose as a source of energy for cellular respiration, store it as starch for later use, or use it to form more complex molecules such as cellulose.

Question 10

What is the significance of photosynthesis for life on Earth?

Answer 10

Photosynthesis is essential for life on Earth as it is the primary process by which oxygen is produced and energy is transferred from sunlight to living organisms.

Question 11

What is the role of Rubisco in photosynthesis?

Answer 11

Rubisco is responsible for the initial changes to carbon dioxide in the light-independent stage of photosynthesis, initiating the Calvin cycle.

Question 12

What is the main function of the light-dependent stage of photosynthesis?

Answer 12

The light-dependent stage splits water molecules to produce ATP, NADPH, and oxygen.

Question 13

Describe the process of carbon fixation in the Calvin cycle.

Answer 13

Carbon fixation involves the conversion of carbon dioxide (CO2) and RuBP into 3-PGA, facilitated by Rubisco.

Question 14

How do C4 plants minimize photorespiration?

Answer 14

C4 plants spatially separate initial carbon fixation (mesophyll cells) and the Calvin cycle (bundle-sheath cell), reducing the likelihood of Rubisco binding to oxygen.

Question 15

What is the role of PEP carboxylase in C4 plants?

Answer 15

PEP carboxylase fixes atmospheric CO2 into a four-carbon molecule, oxaloacetate, in mesophyll cells.

Question 16

How do CAM plants minimize water loss during photosynthesis?

Answer 16

CAM plants open their stomata at night to take in CO2 and store it as organic acids, allowing them to close their stomata during the day to reduce water loss.

Question 17

Compare C3, C4, and CAM plants in terms of their adaptation to photorespiration.

Answer 17

C3 plants have no specific adaptations, C4 plants spatially separate processes, and CAM plants temporally separate processes to minimize photorespiration.

Question 18

Give examples of each type of photosynthesis: C3, C4, and CAM.

Answer 18

C3: Wheat, rice, trees; C4: Corn, sugarcane, switchgrass; CAM: Cacti, pineapples, orchids.

Question 19

How does temperature influence Rubisco’s affinity for CO2 versus O2?

Answer 19

At regular or low temperatures, Rubisco’s affinity for CO2 is higher, but at higher temperatures, its affinity for O2 increases.

Question 20

What is photorespiration, and why is it considered wasteful for plants?

Answer 20

Photorespiration is a process initiated by Rubisco binding to O2 instead of CO2, leading to the loss of CO2 and energy. It’s wasteful because it reduces photosynthesis and wastes resources.

Question 21

How do C4 and CAM plants differ in their strategies to minimize photorespiration?

Answer 21

C4 plants spatially separate initial carbon fixation and the Calvin cycle, while CAM plants temporally separate these processes.

Question 22

Why are CAM plants particularly suited to hot, dry environments?

Answer 22

CAM plants can close their stomata during the day to conserve water while still performing photosynthesis at night.

Question 23

How do C4 and CAM plants conserve water compared to C3 plants?

Answer 23

C4 and CAM plants can close their stomata during the day to reduce water loss, unlike C3 plants, which keep their stomata open during the day.

Question 24

What are some examples of plants that use CAM photosynthesis?

Answer 24

Examples include cacti, pineapples, and orchids.

Question 25

What are the factors that affect the rate of photosynthesis?

Answer 25

Light availability, water availability, temperature, and carbon dioxide concentration.

Question 26

What is the optimal temperature for enzymes involved in photosynthesis?

Answer 26

The optimal temperature for enzymes impacts the rate of photosynthesis.20-35

Question 27

How does light intensity affect the rate of photosynthesis?

Answer 27

The rate of photosynthesis increases with light intensity until it plateaus, either reaching maximum saturation or due to another limiting factor.

Question 28

What happens after the rate of photosynthesis plateaus?

Answer 28

After the plateau, the rate of photosynthesis remains high but constant, indicating either maximum saturation or the influence of another limiting factor.

Question 29

What are the two reasons for the plateau in the rate of photosynthesis?

Answer 29

Either the maximum rate of photosynthesis is reached, or another factor becomes the limiting factor.

Question 30

How does temperature affect the rate of photosynthesis?

Answer 30

Enzymes function optimally at specific temperatures, influencing the rate of photosynthesis. High temperatures can denature enzymes, leading to a decrease in the rate of photosynthesis.

Question 31

How does pH affect the rate of photosynthesis?

Answer 31

Enzymes function optimally at specific pH levels. Deviation from the optimal pH can denature enzymes, affecting the rate of photosynthesis.

Question 32

What is the effect of carbon dioxide concentration on the rate of photosynthesis?

Answer 32

As carbon dioxide concentration increases, the rate of photosynthesis increases until it plateaus, influenced by either maximum saturation or another limiting factor.

Question 33

How does water availability influence the rate of photosynthesis?

Answer 33

Water availability affects stomatal opening and closing, which in turn affects the uptake of carbon dioxide and the release of oxygen, impacting the rate of photosynthesis.

Question 34

What role do enzyme inhibitors play in photosynthesis?

Answer 34

Enzyme inhibitors can reduce the rate of photosynthesis by binding to enzymes involved in the process, hindering their function

Question 35

What is CRISPR-Cas9 and how does it function?

Answer 35

CRISPR-Cas9 is a genetic editing tool found in bacteria. CRISPR consists of detectable DNA sequences, while Cas9 is an endonuclease that cuts and glues DNA together. Cas9 is guided by CRISPR to target specific DNA sites for editing.

Question 36

Why is there a need to improve photosynthetic efficiencies and crop yields?

Answer 36

Increasing agricultural productivity is crucial due to the rising global population and the impact of climate change on crop yields. By 2050, agricultural productivity needs to double, but arable land is already largely exhausted.

Question 37

How can CRISPR-Cas9 technologies improve photosynthetic efficiencies and crop yields?

Answer 37

CRISPR-Cas9 can edit crop genomes to bypass photorespiration, improve Rubisco function, enhance chloroplast efficiency, and target stomata to reduce water stress. It can also modify plants to increase tolerance to harsh conditions.

Question 38

What are some potential applications of CRISPR-Cas9 in agriculture?

Answer 38

CRISPR-Cas9 can be used to increase crop productivity by engineering plants for drought and frost tolerance, disease resistance, and enhanced nutritional value. It can also modify genes related to hormones to increase grain yield.

Question 39

Describe the steps involved in researching the appropriateness of CRISPR-Cas9 applications for improving crop photosynthesis.

Answer 39

Researchers first understand the photosynthetic process of the target crop, model inefficiencies using computers, and then use CRISPR-Cas9 to edit genes responsible for inefficiencies. Applications must adhere to GMO standards and regulations before being commercialized.

Question 40

Provide examples of recent agricultural applications of CRISPR-Cas9.

Answer 40

Recent studies have used CRISPR-Cas9 to increase rice grain yield by targeting genes related to hormone responses, improve Rubisco function in tobacco plants, extend the shelf life of mushrooms, and produce low-gluten wheat for individuals with celiac disease.